Calculate wheel torque per driven wheel from engine torque, gear ratio, final drive, efficiency, and driven wheels. Add tire diameter to estimate tractive force at the ground.
Assumptions & Formulas
Wheel Torque (per wheel) = (Engine Torque × Gear Ratio × Final Drive Ratio × (Efficiency / 100)) / Driven Wheels
Tractive Force Formula:
Tractive Force (per wheel) = Wheel Torque (per wheel) / Tire Radius
Note: Drivetrain efficiency accounts for parasitic losses in the transmission and differential. Typical values range from 80% to 90%. Results are rounded to 2 decimal places.
This wheel torque calculator estimates the actual torque delivered to each driven wheel based on engine torque, transmission gear ratio, final drive ratio, drivetrain efficiency, and the number of driven wheels. To be clear, this tool calculates drive wheel torque from engine torque to measure drivetrain power transfer, not the torque spec needed to tighten your wheel lug nuts.
If you enter an optional tire diameter, the calculator also returns the tractive force per driven wheel. The tool supports quick unit conversions, letting you easily translate engine torque to wheel torque using Nm, lb-ft, or kg-m, while estimating tractive force in N, lbf, or kgf depending on your preferred reference standard.
What this wheel torque calculator calculates
This tool calculates the mechanical multiplication of torque as it moves from the engine or motor through the transmission and differential, down to the ground. It provides a theoretical straight-line estimate of pulling power, not a dynamic traction-limit simulator.
The results show per-driven-wheel torque rather than total combined axle torque. It assumes an equal power split across all active driven wheels, making it a great fit for FWD, RWD, AWD/4WD, motorcycles, or even EV motor torque substitution. You can also view the optional per-driven-wheel tractive force, which represents the actual push at the tire contact patch.
| Tool function | What the calculator returns |
|---|---|
| Wheel torque | Torque at each driven wheel after gear reduction, final drive, efficiency, and wheel split |
| Tractive force | Force at each driven wheel based on wheel torque and tire radius |
| Torque conversion | Nm, lb-ft, kg-m |
| Tire size conversion | in, mm, cm |
| Force conversion | N, lbf, kgf |
Wheel torque formula used in this calculator
The calculations rely on these standard drivetrain multiplication equations:$$\text{Wheel torque per driven wheel} = \frac{\text{Engine torque} \times \text{Gear ratio} \times \text{Final drive ratio} \times \text{Efficiency}}{\text{Driven wheels}}$$$$\text{Tractive force per driven wheel} = \frac{\text{Wheel torque}}{\text{Tire radius}}$$
Here is how each variable functions within the math:
- Engine torque: The base rotational force produced by the engine or electric motor.
- Transmission gear ratio: The active gear reduction multiplier for your selected transmission gear.
- Final drive ratio: The differential or axle ratio multiplier.
- Drivetrain efficiency: The percentage of power retained after mechanical losses through gears and bearings.
- Number of driven wheels: The count of wheels putting power to the ground, dividing the total output.
- Tire radius: Half of the tire diameter, used to convert rotational torque into linear push.
| Variable | Meaning | Required |
|---|---|---|
| Engine torque | Input torque from engine or motor | Yes |
| Transmission gear ratio | Active gear reduction | Yes |
| Final drive ratio | Differential or axle ratio | Yes |
| Drivetrain efficiency | Percent of torque retained after losses | Yes |
| Driven wheels | 1, 2, or 4 | Yes |
| Tire diameter | Used to calculate tractive force | Optional |
How to calculate wheel torque from engine torque
Finding your exact wheel torque requires a simple step-by-step path through the drivetrain.
- Enter your engine torque.
- Enter your current transmission gear ratio.
- Enter your final drive ratio.
- Enter your estimated drivetrain efficiency.
- Choose the number of driven wheels.
- Read the resulting wheel torque per driven wheel.
- Add your tire diameter if you want to see tractive force.
Worked Example Imagine a rear-wheel drive car with the following specs:
- Engine torque: 300 Nm
- Gear ratio: 2.50
- Final drive ratio: 3.73
- Efficiency: 85%
- Driven wheels: 2
- Tire diameter: 26 in
First, find the total reduced torque before the wheel split: 300 × 2.50 × 3.73 × 0.85 = 2377.88 Nm. Next, divide by the 2 driven wheels for the per-wheel torque: 2377.88 / 2 = 1188.94 Nm. To find force, convert the tire diameter to a radius in meters (13 inches = 0.3302 meters). Finally, divide the wheel torque by the radius for the per-wheel tractive force: 1188.94 / 0.3302 = 3600.66 N.
Inputs this wheel torque calculator uses
The tool requires specific numeric values to process the equations. The calculator will reset and wait to show outputs until all required fields are filled, and the tractive force result remains hidden until a tire diameter is entered.
| Input | Accepted format | Notes |
|---|---|---|
| Engine torque | Number + Nm, lb-ft, or kg-m | Must be 0 or higher |
| Transmission gear ratio | Positive number | Must be greater than 0 |
| Final drive ratio | Positive number | Must be greater than 0 |
| Drivetrain efficiency | Percent | Must be greater than 0 and up to 100 |
| Number of driven wheels | 1, 2, or 4 | Determines per-wheel split |
| Tire diameter | Number + in, mm, or cm | Optional, needed for force |
Outputs and units
Depending on your region or the specific specification sheet you are reading, you may need different units.
| Output | Available units |
|---|---|
| Wheel torque per driven wheel | Nm, lb-ft, kg-m |
| Tractive force per driven wheel | N, lbf, kgf |
You can switch units freely. Many users prefer Nm for engineering and SI work, while lb-ft is highly common for automotive specs in North America. The kg-m unit is often helpful where legacy or regional manufacturer specs apply. For force, N, lbf, and kgf are available depending on your baseline reference.
Unit conversions used by the calculator
When you switch between measurement systems, the tool applies these exact conversion constants behind the scenes.
| Conversion | Value |
|---|---|
| 1 lb-ft | 1.35581795 Nm |
| 1 kg-m | 9.80665 Nm |
| 1 in | 0.0254 m |
| 1 mm | 0.001 m |
| 1 cm | 0.01 m |
| 1 N | 0.224808943 lbf |
| 1 kgf | 9.80665 N |
Wheel torque vs tractive force
It is common to mix up these two concepts. Wheel torque is the rotational force twisting the wheel hub. Tractive force is the actual straight-line push created at the tire contact patch where the rubber meets the road.
Because force is calculated using the tire radius as a lever arm, smaller tire radii increase the pushing force for the exact same amount of torque. Conversely, a larger tire radius reduces the pushing force.
| If this changes | Wheel torque | Tractive force |
|---|---|---|
| Higher gear ratio | Increases | Increases |
| Higher final drive ratio | Increases | Increases |
| Higher efficiency | Increases | Increases |
| More driven wheels | Decreases per wheel | Decreases per wheel |
| Larger tire diameter | No change | Decreases |
| Smaller tire diameter | No change | Increases |
FWD, RWD, AWD, and motorcycle wheel torque
The number of driven wheels fundamentally changes how much twist each axle shaft handles.
| Drivetrain type | Driven wheels used in calculator |
|---|---|
| Motorcycle / single-wheel drive | 1 |
| Front-wheel drive | 2 |
| Rear-wheel drive | 2 |
| All-wheel drive / four-wheel drive | 4 |
This tool assumes a perfectly equal torque split across the selected driven wheels in straight-line conditions. It does not factor in dynamic torque vectoring, limited-slip differential bias, or cornering loads.
How tire diameter affects tractive force
The calculator automatically converts your entered tire diameter into a radius because the formula for force requires it: tractive force equals wheel torque divided by tire radius.
Putting the same torque through a smaller tire gives you a higher tractive force. Putting that same torque through a larger tire results in a lower tractive force. It is important to remember that changing your tire diameter does not change the actual wheel torque output from the hub; it only changes the resulting straight-line force.
Assumptions and limitations of this calculator
To provide clear math, this tool relies on a few mechanical baseline assumptions:
- It assumes an equal torque split across all driven wheels.
- It models a pure straight-line acceleration condition.
- It assumes zero clutch slip or torque-converter slip.
- Drivetrain efficiency is a flat, user-estimated percentage, not a dynamically modeled friction curve.
- It does not model traction limits, tire slip, weight transfer, or differential biasing.
- Tire diameter is used purely as a rigid radius-based approximation to find force, ignoring tire squat under load.
When to use this wheel torque calculator
This logic is best suited for direct mechanical comparisons rather than vehicle performance simulations. Use it to:
- Compare wheel torque in different transmission gears.
- Compare how final drive ratio changes alter hub twist.
- Estimate the effect of drivetrain friction loss.
- Estimate per-wheel tractive force from different tire sizes.
- Compare the per-wheel split on a motorcycle vs FWD/RWD vs AWD setups.
- Estimate EV motor torque at the wheel by using the electric motor’s torque as the primary input.
Wheel torque example table
Here is a look at how different gearing, wheel setups, and ratios impact the final numbers, assuming a constant input of 300 Nm engine torque and 85% efficiency.
| Engine torque | Gear ratio | Final drive | Efficiency | Driven wheels | Tire diameter | Wheel torque per wheel | Tractive force per wheel |
|---|---|---|---|---|---|---|---|
| 300 Nm | 2.50 | 3.73 | 85% | 2 | 26 in | 1188.94 Nm | 3600.66 N |
| 300 Nm | 2.50 | 3.73 | 85% | 4 | 26 in | 594.47 Nm | 1800.33 N |
| 300 Nm | 3.50 | 3.73 | 85% | 2 | 26 in | 1664.51 Nm | 5040.92 N |
| 300 Nm | 2.50 | 4.10 | 85% | 2 | 26 in | 1306.88 Nm | 3957.83 N |
Wheel torque calculator FAQ
How do you calculate wheel torque from engine torque?
You calculate it by multiplying engine torque by the transmission gear ratio, final drive ratio, and drivetrain efficiency, then dividing that total by the number of driven wheels.
What is the formula for tractive force from wheel torque?
Tractive force per driven wheel equals the wheel torque per driven wheel divided by the tire radius.
Does this calculator show torque per wheel or total axle torque?
It shows the torque per driven wheel.
Why does the number of driven wheels change the result?
Because the tool splits the total delivered torque equally across 1, 2, or 4 driven wheels, reducing the load on each individual wheel as the count goes up.
Does tire diameter change wheel torque?
No. Changing tire diameter changes the tractive force at the ground, but the actual rotational wheel torque at the hub remains the same.
What drivetrain efficiency should I use?
The tool accepts any value above 0 and up to 100. You should use your own estimate based on your specific drivetrain type, transmission style, and measured parasitic losses.
Can I use this wheel torque calculator for EVs?
Yes, simply enter the EV motor torque as the input torque, keeping in mind that EVs often use a single-speed reduction gear instead of a multi-gear transmission.
Is wheel torque the same as lug nut torque?
No. This calculator measures drivetrain wheel torque (the twisting force turning the wheels to move the car). It is not for wheel fastening torque, which is the static pressure used to safely tighten your lug nuts.
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